Method of Detailed PIONA Analysis in Gasoline Samples Using Hybrid GCxGC-MDGC
Publication Date: 2016-Apr-14
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METHOD OF DETAILED PIONA Analysis in Gasoline Samples Using Hybrid GC×GC-MDGC
This article discloses a new instrumental setup and method for detailed PIONA analysis that utilizes a hybrid GC×GC-MDGC technique.
As general background, gas chromatography (GC) entails the analytical separation of a vaporized or gas-phase sample that is injected into a chromatographic column. The column is typically a metal, glass, or quartz tube containing a stationary phase (a coating or packing) formulated for chromatographic activity. The column is typically housed in a thermally controlled oven or may be heated directly by a heating element such as a resistive wire. A chemically inert carrier gas, such as helium, nitrogen, argon, or hydrogen, is utilized as the mobile phase for elution of the analyte sample in the column. Typically, the sample and carrier gas are separately introduced into a GC inlet coupled to the column head. In the GC inlet, the sample is injected into the carrier gas stream and the resulting sample-carrier gas mixture flows through the column. During column flow the sample encounters the stationary phase in the column, which causes different components of the sample to separate according to different affinities with the stationary phase. The separated components elute from the column exit and are measured by a detector, producing data from which a chromatogram or spectrum identifying the components may be constructed.
A single GC column (one-dimensional GC) may be inadequate for separating a target compound from a sample. In this case, a multidimensional (MDGC) GC system including two or more GC columns and respective downstream detectors, or a comprehensive two-dimensional (GC×GC) system, may be utilized. The different GC columns may have different characteristics such as length, inside diameter, and/or type of stationary phase material. For example, one column may include a polar stationary phase while the other column includes a nonpolar stationary phase. During an appropriate interval of time, a portion of the effluent from the first column containing a target compound may be diverted into the second column and ultimately to the corresponding second detector by implementing a heart-cutting technique.
The detailed analysis of chemical composition of gasoline is required for refinery processes monitoring and for product specifications. Attempts to obtain detailed hydrocarbon analysis (DHA) of gasoline and refining products started in the 1970s using GC techniques. However, it was found that one-dimensional GC lacks peak capacity for mixtures containing compounds above C9 for straight run and exhibited even less peak capacity for mixtures containing high levels of olefins. In order to improve the peak capacity, multidimensional gas chromatographic systems were investigated. In particular, PNA (paraffins, napthenes, and aromatics) and PIONA (paraffins, isoparaffins, olefins,...